Inorganic/organic dispersant and application thereof

ABSTRACT

The present invention discloses an inorganic/organic mixed component (I/O) dispersant and applications thereof, which is primarily applied to dispersing nanoparticles of metal oxides. The I/O dispersant of the present invention can be a composite of inorganic clay and an organic surfactant, a composite of inorganic clay and polyoxyalkylene-amine, or a composite of inorganic clay, polyisobutylene succinic anhydride (PIB-SA) and hydrochloric acid salt or tetraalkyl quaternary salt of polyoxyalkylene-amine, or fatty amines. By mixing with the I/O dispersant of the present invention, nanoparticles of a metal oxide can be uniformly dispersed without aggregation particularly at high solid content. The dispersion has a lower viscosity and is relatively stable in storage even at high temperature.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an I/O (inorganic/organic) dispersantand applications thereof, and particularly to an I/O dispersant which isapplied to dispersing nanoparticles of metal oxides, for example, whitepigment and photocatalyst made from TiO₂.

2. Related Prior Arts

For application of TiO₂ in commercial articles and industrial processes,it's always a technical issue to efficiently disperse TiO₂ particles orpowders into a solvent. Different sizes of TiO₂ can be applied todifferent fields, for example, nanoparticles of TiO₂ can be used asphotocatalysts, microparticles of TiO₂ can be used as paints.

The well known method for dispersing TiO₂ consists in adding a generalorganic surfactant or a polymeric dispersant. The surfactant ordispersant primarily includes different segments with respectiveaffinities to the solvent and the dispersed particles, so that thedispersant can be effectively attached to surfaces of the TiO₂ particlesand also dispersed in the solvent. By means of steric hindrance of thedispersant, the TiO₂ particles will be stable and no longer aggregate inthe solvent.

However, the effect of the dispersant is easily influenced bytemperature and time. Once the dispersant is desorbed or isolated fromthe surfaces of the TiO₂ particles, the dispersant will be unstable withaggregation.

To solve the above problem, the present invention provides an I/Odispersant which is suitable for application of TiO₂ particles.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an I/O dispersant,which can effectively disperse nanoparticles of a metal oxide.

Another object of the present invention is to provide a method fordispersing nanoparticles of a metal oxide by applying the aforementionedI/O dispersant, so that the nanoparticles can be uniformly dispersed.

To achieve the above objects, the I/O dispersant of the presentinvention can be a composite of inorganic clay and an organicsurfactant; and the I/O dispersant is produced by reacting the inorganicclay with the organic surfactant.

The I/O dispersant of the present invention can also be a composite ofinorganic clay and polyoxyalkylene-amine; and the I/O dispersant isproduced by reacting the inorganic clay with the polyoxyalkylene-amine.

The I/O dispersant of the present invention can further be a compositeof inorganic clay, polyisobutylene succinic anhydride (PIB-SA,Mw=300˜2000 g/mol) and polyoxyalkylene-amine; and the I/O dispersant isproduced by reacting the inorganic clay with PIB-SA grafted withpolyoxyalkylene-amine.

The I/O dispersant of the present invention can be produced by reactingthe inorganic clay with fatty amine quaternary ammonium salt of C12˜C32.

In the present invention, the method for dispersing nanoparticles of ametal oxide comprises mixing the I/O dispersant and the nanoparticles ofthe metal oxide.

The I/O dispersant of the present invention can be used for dispersingsuch metal oxides as SiO₂, Fe₂O₃, Al₂O₃, ZrO, Ag₂O, TiO₂, etc.

The above inorganic clay is preferably in the form of layers or sheets,and can be natural clay of silicate and aluminum oxide (for example,natural montmorillonite), organoclay (prepared from organic surfactantintercalated clay through ionic salt exchanging), exfoliated clay (forexample, nanosilicate platelets), synthetic fluoride mica, syntheticnanoclay (SNC) or other proper inorganic clays (for example, K10,layered double hydroxides (LDH), kaolin, bentonite, synthetic layeredclay, talc, attapulgite clay, laponite, vermiculite, etc.)

The organic surfactant of the present invention can be a cationicsurfactant, a nonionic surfactant or an amphoteric surfactant; forexample, fatty amine quaternary ammonium salt of C12˜C32, HCl amine saltof C12˜C32, alkylphenol ethoxylate or fatty alcohol ethoxylate. Thepreferred organic surfactant is octadecyl amine (ODA) or other alkylamine salts and quaternary salts. For the resultant dispersant, theorganic surfactant and the inorganic clay preferably have anorganic/inorganic ratio of about 10/90˜90/10.

In the present invention, polyoxyalkylene-amine has a molecular weightof about 200˜10,000. One of this series of products, the Jeffamine®Amine series products, is commercially produced by Huntsman Co. Forexample, Jeffamine® diamine D-230, D-400, D-2000, D-4000, and ED-2003.Polyoxyalkylene-amine and the inorganic clay preferably have a cationexchanging capacity (CEC) ratio of about 0.1˜1.0. For the resultantdispersant, the polyoxyalkylene-amine and the inorganic clay preferablyhave an organic/inorganic ratio of about 55/45˜99/1.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the reaction for grafting PIB-SA withpolyoxyalkylene-amine.

FIG. 2 shows the status of the TiO2 particles dispersed in a solventwith D2000/MMT as the dispersant (b), ODA/NSP as the dispersant (c), andwithout any dispersant (a).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The intercalated inorganic clay of the present invention can be preparedby referring to R.O.C. (Taiwan) Patent No. 254064 and Pub. Nos. 550246and 577904. The nanosilicate platelets of the present invention can beprepared by referring to R.O.C. Patent Nos. 280261, 284138 and 270529,and Pub. Nos. 577904 and 593480. The other materials used in thepreferred embodiments (Examples) include:

1. Montmorillonite: Na⁺-MMT, a product of Nanocor Ind. Co. (CEC=1.2mequiv/g) and a product of Kunimine Ind. Co. (Kunipia-F, CEC=1.15mequiv/g).

2. Synthetic Nanoclay: SNC, a product of CO-OP Chemical Co., LTD(CEC=0.7˜1.2 mequiv/g).

3. Polyoxyalkylene-amine: Jeffamine® series products of HuntsmanChemical Co., for example, D-2000, T-403, T-5000; wherein D-2000(poly(propylene glycol) bis(2-aminopropyl ether), Mw=2000) has astructural formula:

4. TiO₂: nanoparticles, a product of BASF and Aldrich Chemical Co.

EXAMPLE 1

Step (a): Na⁺-montmorillonite (MMT) (10 g) is first dispersed in water(1 L) at 80° C. and then vigorously stirred for 4 hours to obtain astable earth-colored dispersion.

Step (b): The polyoxypropylene diamine of Mw 2000 (D2000) (24 g, 12mmol, CEC ratio of D2000/MMT=1.0) is dissolved in ethanol (100 ml), andequivalent moles of hydrochloric acid is added therein for acidificationfor 30 minutes. The acidified intercalation solution is added to theNa⁺-MMT dispersion slowly and stirred at 60˜70° C. for 6 hours for acation exchanging reaction. Then the resultant reaction solution isseparated into two phases. After filtration, the residual is washed withwater for several times to remove the unreacted organics and theinorganic clay. The synthesized product (D2000/MMT hybrid) was analyzedto have an organic/inorganic weight ratio 74/26 and can be further driedin a vacuum oven at high temperature for 24 hours.

EXAMPLES 2˜3, COMPARATIVE EXAMPLES 1˜2

Repeat the steps of Example 1, but the dosage of D2000 is changed sothat CEC=0.8, CEC=0.6, CEC=0.4, and CEC=0.2, respectively. The products(D2000/MMT) with organic/inorganic weight ratios 69/31, 63/37, 53/47,and 36/64 are obtained.

EXAMPLE 4

Step (a): Na⁺-MMT (10 g) is first dispersed in water (10 L) at 80° C.and then vigorously stirred for 4 hours to obtain a stable earth-coloreddispersion.

Step (b): P-cresol (27.2 g) and D2000 (757.6 g) are weighted with amolar ratio 2:3 and circulated in toluene at 90° C. for 3 hours. Then aformaldehyde solution (37 wt %, 61.4 g) is added and the temperature israised to 130° C. for reaction for 5 hours. When a gel is formed, thereaction is stopped and the product, an intercalating agent AMO(Amine-termination Mannich Oligomer), can be obtained. The AMO isanalyzed with GPC and three peaks are found at Mw=3,142, 6,221 and9,246, respectively. Results of amino titration are that primaryamine=0.4 meq/g, secondary amine=0.56 meq/g, and no tertiary amine isfound. Then the AMO is dissolved into water (575 g) and mixed withconcentrated hydrochloric acid (35 wt %, 36 g) at 80° C. for 30 minutesto acidify the AMO. The acidified AMO is poured into the above Na⁺-MMTdispersion and vigorously stirred at 80° C. for 5 hours. After theintercalation reaction is completed, a mixture solution of AMO/Clay isobtained.

Step (c): A buffer solution of water at various pH values is added intothe mixture solution of AMO/Clay which then becomes a yellowishemulsification slurry.

Step (d): Ethanol (7.5 L) is added into the slurry. After filtration,the residual is added into ethanol (10 L) and stirred. After filtration,a semi-opaque yellowish mixture of AMO/MMT platelet silicates isobtained with an organic/inorganic (O/I) ratio of about 40/60.

Step (e): The AMO/MMT mixture is added into ethanol (10 L) and stirredwell. After water (10 L) is added and stirred well and then toluene (10L) is then added and stirred well. After it is left to stand for oneday, the mixture solution is separated into three phases, wherein theupper phase includes toluene and AMO, the middle phase includes ethanol,and the lower phase includes the product, a water solution of NSP.

Step (f): Octadecyl amine (ODA) and a water solution of NSP are mixedwith an organic/inorganic weight ratio of 70/30 for modification of thenanosilicate platelets. After drying, an I/O dispersant (ODA/NSP) isobtained.

COMPARATIVE EXAMPLE 3

Repeat the steps of Example 4, but ODA and the water solution of NSP aremixed with an organic/inorganic weight ratio of 30/70 in Step (f).

EXAMPLE 5

Repeat Step (a) and Step (f) of Example 4, but NSP is replaced with MMTin Step (f). Then the product (ODA/MMT) with an organic/inorganic weightratio 70/30 is obtained.

EXAMPLE 6

Repeat Step (a) and Step (f) of Example 4, but MMT of Step (a) and NSPof Step (f) are replaced with synthetic nanoclay (SNC). Then the product(ODA/SNC) with an organic/inorganic weight ratio 70/30 is obtained.

EXAMPLE 7

Repeat Step (a) and Step (f) of Example 4, but MMT of Step (a) and NSPof Step (f) are replaced with synthetic mica. Then the product(ODA/Mica) with an organic/inorganic weight ratio 70/30 is obtained.

EXAMPLES 8˜12

Repeat the procedure in the R.O.C. (Taiwan) Patent No.574370 “CombinedAntifoulant of Derivative Disperser From Polyetheramine And PIBSA”, sothat PIB-SA-POP or PIB-SA-POE can be obtained by grafting hydrophobicpolyisobutylene succinic anhydride (PIB-SA) with Jeffamine® diamineD-230 (or POP230), D-400 (or POP400), D-2000 (or POP2000), D-4000 (orPOP4000), and ED-2003 (or POE2000). The reaction is shown in FIG. 1. TheI/O dispersants are obtained by respectively mixing these PIB-SA-POP orPIB-SA-POE with clay.

Evaluation of Dispersants and Dispersions 1. Dispersions of Examples 17and Comparative Examples 13

The modified clay is uniformly dispersed in heptane to have aconcentration of 1˜30 wt. %. Then TiO₂ (10 wt. % or 50 wt. %) are addedfor dispersion. Effects of the dispersants are evaluated by observing ormeasuring the mobility and the uniformity of the dispersions with aviscometer, SEM, TEM, AFM, and an interfacial tension meter areprovided. Results are listed in Table 1.

TABLE 1 Example/ Organic/ Effect for Comparative CEC inorganicdispersing TiO₂ Example Dispersant ratio Weight ratio 10 wt. % 50 wt. %Examples 1 D2000/MMT 1.0 74/26 + − Examples 2 D2000/MMT 0.8 69/31 + −Examples 3 D2000/MMT 0.6 63/37 + − Comparative D2000/MMT 0.4 53/47 − −Examples 1 Comparative D2000/MMT 0.2 36/64 − − Examples 2 Examples 4ODA/NSP — 70/30 + + Comparative ODA/NSP — 30/70 − − Examples 3 Examples5 ODA/MMT — 70/30 + + Examples 6 ODA/SNC — 70/30 + − Examples 7 ODA/Mica— 70/30 + −

As shown in Table 1, the products D2000/MMT of Examples 1˜3 caneffectively disperse TiO₂ (10 wt. %), but those of Comparative Examples1˜2 can not. As for high solid content of TiO₂ (50 wt. %), none of theproducts D2000/MMT can disperse them well.

In Example 4, the product ODA/NSP with an organic/inorganic weight ratio70/30 can effectively disperse TiO₂ (both 10 wt. % and 50 wt. %).However, when the organic/inorganic weight ratio is 30/70 as inComparative Example 3, even TiO₂ (10 wt. %) can not be dispersed well.

In Example 5, the product ODA/MMT exhibits effect for dispersing TiO₂ asgood as in Example 4. Both TiO₂ of 10 wt. % and 50 wt. % can bedispersed well.

In Comparative Examples 6 and 7, though the products ODA/SNC andODA/Mica have higher organic/inorganic weight ratio 70/30, only TiO2 (10wt. %) can be dispersed well.

FIG. 2 compares dispersions of TiO₂ (20 wt. % in hexane) with andwithout dispersant, and with different dispersants. Picture (B) showsthe bottles of picture (A) upside down, wherein no dispersant is addedin the bottle (a), D2000/MMT (10 wt. %) is added in the bottle (b), andODA/NSP (10 wt. %) is added in the bottle (c). the results show thatODA/NSP (10 wt. %) results in the best mobility and uniformity, that is,the dispersion has a lowest viscosity. The dispersion includingD2000/MMT (10 wt. %) is not as good as that of bottle (c), but muchbetter than that of bottle (a) without adding the dispersant.

2. Dispersions of Examples 8˜12

The I/O dispersants including PIB-SA-POP and PIB-SA-POE are firstuniformly dispersed in methyl cyclohexane to have a concentration of 10wt. %. Then different concentrations of TiO₂ (10 wt. % and 50 wt. %) areadded for dispersion. Effects of the dispersants are evaluated byobserving or measuring the mobility and the uniformity of thedispersions. Results shows that both PIB-SA-POP and PIB-SA-POE (10 wt.%) perform well in dispersion and are suitable for processes with a lowdosage.

In the present invention, the organic layered clay greatly facilitatesdispersion of TiO₂ in organic solvents when modified with organicsurfactants or polyoxyalkylene-amine. By means of steric hindrance,different nanoparticles with different geometric shapes can reduce orcountervail the energy thereof. For example, white TiO₂ pigmentparticles or photocatalysts can be dispersed by the natural clay havinga layered structure. Such mechanism using a geometric principle is notrelated to adsorption or desorption, and thus thermal stability ofdispersions will be improved.

In the present invention, the layered clay is modified to have ahydrophobic end, and therefore can serve as a dispersant withoutaggregation. The modified clay can promote mobility and stability ofhigh-concentration dispersions of TiO₂, wherein the nanosilicateplatelets (NSP) with a high aspect ratio (average 100×100×1 nmdimension), high surface area (700˜800 m²/g) and high charge density(20,000 ions/platelet) is particularly preferred. Accordingly,properties or characteristics of the dispersion, for example, lowerviscosity, better thermal, UW and pH stability, are improved and thussuitable for many applications.

1. An inorganic/organic (I/O) dispersant for dispersing a metal oxide,comprising a composite of an inorganic clay and an organic surfactant,or a composite of inorganic clay and polyoxyalkylene-amine, wherein theorganic surfactant is a cationic surfactant, a nonionic surfactant or anamphoteric surfactant; the inorganic clay is in the form of layers orsheets; and polyoxyalkylene-amine has a molecular weight of 200˜10,000.2. The I/O dispersant as claimed in claim 1, wherein the metal oxide isselected from the group consisting of SiO₂, Fe₂O₃, Al₂O₃, ZrO, Ag₂O andTiO₂.
 3. The I/O dispersant as claimed in claim 1, wherein the organicsurfactant is a fatty amine quaternary ammonium salt of C12˜C32, an HClamine salt of C12˜C32, a tetraalkyl quaternary salt of C12˜C32,alkylphenol ethoxylate or fatty alcohol ethoxylate.
 4. The I/Odispersant as claimed in claim 1, wherein the organic surfactant and theinorganic clay has an organic/inorganic weight ratio of 10/90˜90/10. 5.The I/O dispersant as claimed in claim 1, wherein the inorganic clay isnatural clay of silicate and aluminum oxide, exfoliated clay, syntheticmica or synthetic nanoclay.
 6. The I/O dispersant as claimed in claim 1,wherein the polyoxyalkylene-amine is a Jeffamine® Amine series productof Huntsman Chemical Co.
 7. The I/O dispersant as claimed in claim 1,wherein the polyoxyalkylene-amine and the inorganic clay have a cationexchanging capacity ratio of 0.1˜1.0.
 8. The I/O dispersant as claimedin claim 1, wherein the polyoxyalkylene-amine and the inorganic clayhave an organic/inorganic weight ratio of 55/45˜99/1.
 9. The I/Odispersant as claimed in claim 1, wherein the polyoxyalkylene-amine isselected from the group consisting of Jeffamine® diamine D-230, D-400,D-2000, D-4000 and ED-2003.
 10. The I/O dispersant as claimed in claim1, wherein the composite of inorganic clay and polyoxyalkylene-aminefurther comprises polyisobutylene succinic anhydride (PIB-SA).
 11. Amethod for producing an inorganic/organic (I/O) dispersant fordispersing a metal oxide, comprising a step of reacting inorganic claywith an organic surfactant, or reacting inorganic clay withpolyoxyalkylene-amine, wherein the organic surfactant is a cationicsurfactant, a nonionic surfactant or an amphoteric surfactant; theinorganic clay is in the form of layers or sheets; and thepolyoxyalkylene-amine has a molecular weight of 200˜10,000.
 12. Themethod as claimed in claim 11, wherein the metal oxide is selected fromthe group consisting of SiO₂, Fe₂O₃, Al₂O₃, ZrO, Ag₂O and TiO₂.
 13. Themethod as claimed in claim 11, wherein the organic surfactant is a fattyamine quaternary ammonium salt of C12˜C32, an HCl amine salt of C12˜C32,a tetraalkyl quaternary salt of C12˜C32, alkylphenol ethoxylate or fattyalcohol ethoxylate.
 14. The method as claimed in claim 11, wherein theorganic surfactant and the inorganic clay have an organic/inorganicweight ratio of 10/90˜90/10.
 15. The method as claimed in claim 11,wherein the inorganic clay is natural clay of silicate and aluminumoxide, exfoliated clay, synthetic mica or synthetic nanoclay.
 16. Themethod as claimed in claim 11, wherein the polyoxyalkylene-amine is aJeffamine® Amine series product of Huntsman Chemical Co.
 17. The methodas claimed in claim 11, wherein the polyoxyalkylene-amine and theinorganic clay have a cation exchanging capacity ratio of 0.1˜1.0. 18.The method as claimed in claim 11, wherein the polyoxyalkylene-amine andthe inorganic clay have an organic/inorganic weight ratio of 55/45˜99/1.19. The method as claimed in claim 11, wherein the polyoxyalkylene-amineis Jeffamine® diamine D-230, D-400, D-2000, D-4000 or ED-2003 ofHuntsman Chemical Co.
 20. The method as claimed in claim 11, whereinpolyisobutylene succinic anhydride (PIB-SA) is mixed with inorganic clayand polyoxyalkylene-amine in the step of reacting inorganic clay withpolyoxyalkylene-amine.
 21. A method for dispersing nanoparticles of ametal oxide, comprising a step of mixing an inorganic/organic (I/O)dispersant and nanoparticles of the metal oxide, wherein the I/Odispersant is a composite of inorganic clay and an organic surfactant,or a composite of inorganic clay and polyoxyalkylene-amine, wherein theorganic surfactant is a cationic surfactant, a nonionic surfactant or anamphoteric surfactant; the inorganic clay is in the form of layers orsheets, and polyoxyalkylene-amine has a molecular weight of 200˜10,000.22. The method as claimed in claim 21, wherein the metal oxide isselected from the group consisting of SiO₂, Fe₂O₃, Al₂O₃, ZrO, Ag₂O,TiO₂.
 23. The method as claimed in claim 21, wherein the organicsurfactant is a fatty amine quaternary ammonium salt of C12˜C32, an HClamine salt of C12˜C32, a tetraalkyl quaternary salt of C12˜C32,alkylphenol ethoxylate or fatty alcohol ethoxylate.
 24. The method asclaimed in claim 21, wherein the organic surfactant and the inorganicclay have an organic/inorganic weight ratio of 10/90˜90/10.
 25. Themethod as claimed in claim 21, wherein the inorganic clay is naturalclay of silicate and aluminum oxide, exfoliated clay, synthetic mica orsynthetic nanoclay.
 26. The method as claimed in claim 21, wherein thepolyoxyalkylene-amine is a Jeffamine® Amine series product of HuntsmanChemical Co.
 27. The method as claimed in claim 21, wherein thepolyoxyalkylene-amine and the inorganic clay have a cation exchangingcapacity ratio of 0.1˜1.0.
 28. The method as claimed in claim 21,wherein the polyoxyalkylene-amine and the inorganic clay have anorganic/inorganic weight ratio of 55/45˜99/1.
 29. The method as claimedin claim 21, wherein the polyoxyalkylene-amine is Jeffamine® diamineD-230, D-400, D-2000, D-4000 or ED-2003 of Huntsman Chemical Co.
 30. Themethod as claimed in claim 21, wherein the composite of inorganic clayand polyoxyalkylene-amine is further mixed with polyisobutylene succinicanhydride (PIB-SA).